YSZ Bonding Layer for Solid Oxide Fuel Cell Interconnects
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Solution Overview
Problem
Solid oxide fuel cell (SOFC) stacks are susceptible to damage from temperature fluctuations, leading to mechanical stress and limited thermal shock resistance, which results in breakdown and failure, particularly when individual fuel cells are stacked, necessitating an improved bonding layer to enhance their stability and performance.
Innovation Solution
A bonding layer formed from yttria stabilized zirconia (YSZ) powder with a monomodal particle size distribution, where the d50 is greater than 1 μm and d90 is greater than 2 μm, is introduced between the interconnect layer and electrode layers in the SOFC stack to improve bonding and reduce cracking, thereby increasing the Steady State Area Specific Resistance (ASR) over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bonding layers are used in SOFC stacks, then assembly is straightforward, but thermal shock resistance is limited and mechanical stress causes cracking and failure
Solution Approach 1:
The patent changes the particle size distribution parameters of YSZ powder from conventional bimodal or multimodal distributions to a specific monomodal distribution with d50 > 1 μm and d90 > 2 μm. This parameter change in particle size improves thermal shock resistance by creating a more uniform microstructure that better accommodates thermal stress, directly resolving the contradiction between reliability and complexity.
Solution Approach 2:
The patent uses composite material formulation by combining YSZ powder with specific binders and additives to create a bonding layer that achieves enhanced thermal shock resistance. The composite nature of the bonding layer material allows optimization of both mechanical strength and thermal properties without excessive complexity.
2Productivity
If fuel cells are stacked to form assemblies, then productivity increases, but mechanical stress from temperature fluctuations causes breakdown and failure
Solution Approach 1:
The patent applies local quality by providing enhanced bonding layer properties specifically at the critical interfaces between interconnects and electrodes within the stack. The monomodal YSZ powder creates a uniformly dense bonding layer at these local interfaces, which prevents crack propagation and maintains stack stability during thermal cycling, thereby enabling higher productivity without sacrificing reliability.
3Strength
If bonding layers are made with finer particles for better bonding, then bonding strength improves, but thermal shock resistance decreases due to higher porosity
Solution Approach 1:
The patent resolves this contradiction by changing the particle size distribution parameters to a monomodal distribution with d50 > 1 μm and d90 > 2 μm. This specific parameter range achieves an optimal balance where particles are fine enough to provide good bonding strength through effective sintering, yet coarse enough to maintain lower porosity and better thermal shock resistance compared to finer particle sizes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The use of YSZ powder with specific particle size distribution in the bonding layers reduces interconnect cracking and degradation of Area Specific Resistance (ASR), leading to improved long-term electrochemical performance and stability of the SOFC stack, allowing it to reach a Steady State ASR within a time period of not less than 600 hours of operation.
Implementation Method 1
The bonding layer may be formed from a yttria stabilized zirconia (YSZ) powder having a monomodal particle size distribution (PSD) with a d50 that is greater than about 1 μm and a d90 that is greater than about 2 μm
Data Source
AI summary
A bonding layer, disposed between an interconnect layer and an electrode layer of a solid oxide fuel cell article, may be formed from a yttria stabilized zirconia (YSZ) powder having a monomodal particle size distribution (PSD) with a d50 that is greater than about 1 μm and a d90 that is greater than about 2 μm.